Auto Repair Advice by Professional Automotive Experts
How
Does it Work /
Brake
Pads
How Do Brake Pads Work?
Introduction
Brake pads are designed to absorb
heat as they create friction against the brake rotor. The brake pads ride
against either side of the
brake rotor and are held in place by the
brake caliper that is typically mounted to the spindle or backing plate.
Hydraulic pressure is provided by the brake system via a brake master cylinder.
When the brake system is activated the brake pads are forced against the brake
rotor causing it to slow down, in turn slowing the motion of the
car. Heat
is created and dissipated through the brake pad and rotor. If a bake pad or
rotor become overheated it can hinder the brake operation until cooled. Brake
pads are designed to withstand the amount of pressure provided by the master
cylinder. While the backing plates of all brake pads are made of metal there are
several different classifications of the brake composite, for example; organic,
semi metallic and ceramic to name a few. The organic pad is used mainly for
stock applications, the semi metallic is used for trucks and
SUV's
while the ceramic pad is used for race and extreme conditions. Each of these
pads possess individual wear and usage characteristics, for example; organic
pads are the most forgiving pad when it comes to
brake rotor wear, and tend to make less brake noise such as
squeaking. Semi metallic pads tend to be more abusive to the rotors but can
take more heat before brake fade occurs. Ceramic pads are the hardest pad of the
group and will wear out the rotors over the life of the brake pad. Ceramic pads
can also be associated with brake pad producing noises like squeaking, grumbling
and other undesirable noises. The advantage of the ceramic pads is the lifespan
of the brake pad set is about 25% longer than a regular brake pad. Every brake
pad manufacturer has their own mixture of composite material that can vary in
cost and quality. This material is bonded or riveted to the metal backing plate
that is fitted into the
brake caliper.
Front Brake Pads (appearance will vary)
When servicing or replacing brake pads it is advised to wear a breathing mask
over your nose and mouth to avoid inhaling brake dust particles. It is also
advisable to wear gloves to avoid skin irritation. These dust particles have
been known to cause health problems when exposed to them for an extended amount
of time. When replacing brake pad always match the old brake pads to the new
brake pads. The backing plate of the brake pad should be identical to the old
brake pads, except for the missing brake pad composite material. Some brake pads
are fitted with anti rattle clips. These clips are design to allow the brake
pads to move freely within the caliper mount. If these clips are not included
with the brake pad set transfer the old clips to the new brake pads set. Do not
discard the anti rattle clips this will result in the brake pad having excessive
clearance which will create a
pop or
click sound when the brakes are applied. Some brake pad design will include
a screamer style of wear indicator. This minimum thickness indicator was created
to make a "chirping
or screaming noise" when the brakes are in the "idle" position or when the
brakes are applied. In an effort to help keep the brake pad in place
manufacturers have designed "built in" clips that hold the pad to the inside and
outside of the caliper. The inboard pad clip fits inside the caliper piston
while the outboard pad clip attaches to the outer part of the caliper. These
holder clips hold the brake pads to the
brake caliper when it is not bolted to the spindle.
Squeaking or Grumbling Brakes
Brake squeak is one of the most
common problems that can occur when the brakes are in operation. The
brake squeaking noise is caused by ultra small vibrations that develop into
an audible frequency. There are a number of reasons brakes can produce this
noise. The most common cause of brake squeak is cheap or inferior brake pads and
rotors. As in most things in life you get what you pay for, and cheap brake
components are cheap for a reason. They are made using sub-par material and
below average manufacturing techniques. These brake components tend to wear out
more rapidly with below average performance characteristics. There is additional
steps you can take to help insure quite brake operation. When installing new
brake pads use brake pad shims. These shims act as a shock absorber to dampen
brake vibration which will help stop brake squeak. Heat can affect brake pads in
a negative way, if the brake pad has over heated it can cause the composite
material to become crystallized, when crystallization occurs the brake pad
becomes harder. If a brake pad is hardened it can cause brake squeak. Once the
condition has occurred you must replace the brake pads with a new set to repair
the problem. When replacing brake pads you it is advisable to replace or
re-machine the brake rotor. The reason for this is because when a brake is used
over the life of the brake pad it will develop an un-even surface across the
face of the brake rotor. If new brake pads are installed onto a worn
brake rotor it can cause irregular brake operation and squeaking. This can
cause the brake pedal or
steering wheel to pulse when the brakes are in operation.
Replacing a Brake Pads:
- Loosen but (Do Not Remove) the lug nuts of the
wheel to be serviced
- Support car in a safe position high enough to remove the brake rotor and
pads
- Remove the lug nuts and wheel
- Use a pry bar to force the caliper piston into the caliper
- Loosen appropriate nuts and bolts to remove the brake caliper
- Remove the caliper, brake pads and rotor
- Clean all rotor and brake pad mounting surfaces
- Install new brake pads and rotors (or re-machined rotors) and reassemble
- Tighten all caliper mount bolts
- Slowly push the brake pedal down and then up to take up air gap space between
the brake pad and rotor
-
Bleed brake system as needed
(note: if the system was never opened it probably does not need to be bled)
- Inspect brake caliper and hose connection for leaks, if brake fluid leaks
exist repair as needed and bleed system
- Reinstall wheel and lug nuts, lower the tire onto the ground then finish
tightening lug nuts
- NEVER MOVE A CAR WITHOUT NORMAL BRAKE PEDAL OPERATION
Preferred Procedure: When tightening any brake component
including the lug nuts it should be done using a torque wrench, and tightened to
manufactures specifications. For manufacturer replacement guides, service procedures
and torque specifications consult a
car repair manual.
Common Problems
- When replacing a brake caliper make sure the sealing washer is not leaking
- When brake squeak occurs change the brake pads to OEM (original
equipment manufacturer)
How to Replace Front Brake Pads Video
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How to Change Front Brake Pads and Rotors
How Does it Work
/ Brake
Pads
Check Manufacturer Specific Brake
Caliper Question and Answers
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